Aconcert charges $30 admission and $15 per shirt. alyssa paid $75 at the concert for her admission and shirts. write and solve an equation to find the number of shirts alyssa bought. explain what your variable represents. a. let x = number of admission tickets; 30x + 15 = 75; 2 tickets. b. let x = number of admission tickets; 15x + 30 = 75; 3 tickets. c. let x = number of shirts; 30x + 15 = 75; 2 shirts. d. let x = number of shirts; 15x + 30 = 75; 3 shirts.